Hacker News Reader

Comment by whatshisface | Hacker News Reader

I don't get it, how are |> and <| any different from parentheses?

Call/Pipe operators are just sugar for normal function calls. It's nice because adding or removing a call doesn't require balancing parentheses. It's helpful for writing stream or sequence/iterator based code and throwing debug utilities in the middle.

It's less of an issue if your language has UFCS or other postfix function call syntax like mentioned in this thread, but if you don't this is nice to have.

Chaining without nesting.

If you mean without closing parentheses, I think you can also do that in languages like Haskell with non-parenthetical function calls.

I'm not a Haskell user, but my experience with this in the Nix language is a bit mixed. It definitely works sometimes, but then you get a pileup of parenthesis nesting anyway, because the default is greedy and you have to control which functions get which arguments.

Don't $ signs work in Nix the way the work in Haskell?

E.g. https://mmhaskell.com/blog/2021/7/5/function-application-usi...

If so, I've never seen that style used or documented.

It also allows you to invert the order of the calls so they are written in the order they occur. Instead of paint(sand(cut(measure(wood)))), you can write wood | measure | cut | sand | paint, which is easier to read, especially if it splits over multiple lines or has additional arguments:

paint(sand(cut(measure(wood, 12), 40, :WZ), 220), :red)

wood | measure(12) | cut(40, :WZ) | sand(220) | paint(:red)

IIRC you can do that in Haskell as well, but I forget the name of the feature. Many OOP libraries have started to adopt a chained method call style similar to this, but it is nice to be able to do with any function.

In Haskell, if all the functions in the pipeline are pure, I'd probably write that as

    wood
    & measure 12
    & cut 40 WZ
    & sand 220
    & paint Red

See https://hackage.haskell.org/package/base-4.17.0.0/docs/Data-...

Reply on news.ycombinator.com